A rotary laser irradiation system projects a laser beam by rotary irradiation to form a horizontal reference plane or a tilted reference plane tilted with respect to a horizontal plane. Further, a tilt angle of a tilted plane is set with respect to a horizontal reference line, and hence a direction of the reference line (which will be referred to as a tilt direction hereinafter) must be first set.
Referring to FIG. 15, a conventional method of setting a tilt direction of a tilted plane will now be described hereinafter.
In FIG. 15, reference numeral 1 denotes a rotary laser irradiating system, and reference numeral 2 denotes a photodetection device. The rotary laser irradiating system 1 has a rotator 3 for deflecting a laser beam to a horizontal direction and for projecting the deflected laser beam by rotary irradiation, a main unit 4 having a function of emitting the laser beam, of tilting the rotator 3, and of tilting an irradiating direction, and a main unit rotator 5 for rotating the main unit 4 in the horizontal direction. When the laser beam is projected from the rotator 3 by the rotary irradiation, a reference plane 6 is formed.
Further, the photodetection device 2 has a photodetection unit 7 and detects the laser beam transmitted through the photodetection unit 7.
In order to set a tilt direction, the photodetection device 2 is installed in the tilt direction and leveling is performed. Then, the reference plane 6 formed by the laser beam is greatly tilted in the normal and the reverse directions, and a direction of the main unit 4 is aligned in such a manner that a point (a cross point) which does not move at the time of tilting is aimed at the direction of the photodetection device 2.
A line, which connects a rotation center of the rotator 3 with the cross point of the reference planes 6 and 6′, serves as a tilt central line (a trunnion 8 of a tilted plane). Therefore, a direction orthogonal to the trunnion 8 becomes the tilt direction.
When the main unit 4 is rotated 90° by the main unit rotator 5, the main unit 4 is adequately directed to the tilt direction.
When a tilt angle is set in this state, a desired tilted reference plane can be set.
According to the conventional method described above, the rotary laser irradiating system 1 requires the rotator 3 and an angle detector to detect a direction of the main unit 4, and a manufacturing cost of the rotary laser irradiating system 1 increases.
Furthermore, accurately detecting the cross point by using the photodetection device 2 is a very difficult operation, and a long time is required, an operation efficiency is poor, and a burden on an operator is heavy.
Moreover, as disclosed in JP-A-H9-257478 (1997) (Patent Document 1), there is a system having a configuration that the photodetection device 2 reflects the laser beam, the rotary laser irradiating system 1 detects a reflection light and detects a direction of the photodetection device 2 toward the rotary laser irradiating system 1, and the rotary laser irradiating system 1 is arranged to aim at the direction of the photodetection device 2.
However, the system disclosed in Patent Document 1 requires a function of detecting the reflection light from the photodetection device 2, a function of detecting a direction of the rotary laser irradiating system 1 at the time of detection, and a function of setting the direction of the rotary laser irradiating system 1 to the photodetection device 2, and it likewise has a problem of increasing a manufacturing cost of the rotary laser irradiation system 1.
To solve the problem as described above, the present invention can utilize an inexpensive rotary laser irradiating system having a simple configuration to enable easily setting a tilt direction and also enable easily setting a tilted reference plane.